A two-photon fluorescence microscope images through nonlinear effects excited by a fluorescence light. The fluorescent light with a relative short wavelength may be produced by a laser light with a relative long wavelength, such that the two-photon fluorescence microscope has a deep penetration depth and few fluorescence excitations in defocus areas.
The conventional two-photon fluorescence microscope employs a point-scanning manner. However, a scanning speed based on the point-scanning manner decreases as a field of view increases. Therefore, it is hard to rapidly image a large field of view.